1. An expression of emotions; especially, merriment or delight, accompanied by a series of spontaneous facial and bodily movements: The laugh of my friend was exuberant and infectious and soon the whole room was enjoying a good laugh.
2. Something that provokes amusement, or ridicule: After all the advance publicity, the political speech turned out to be a laugh.
3. That which is proven to be ultimately successful after an apparent defeat or loss: Aurora smiled slyly when she completed the race, because she knew she would still have the last laugh on her critics.

Expressing being happy by believing that some comment or act is very amusing and thereby resulting in a loud utterance or outcry: The people in the auditorium were laughing as if they were out of control.

Mary couldn't stop laughing when she saw what Bruce was wearing.

Susan commented, "Come on, Ralph, do you have to laugh so much? Myrna couldn't help dropping the cake when she tripped on the edge of the rug!"

Having made a lot of money; especially, when doing something that other people consider to be foolish: There were those who thought Celeste's investment in the company was stupid, but now she's laughing all the way to the bank.